He and Katara were never far from one another for the days directly after the raid that killed their mother - their father had left on an extended hunting trip, alone, and Grangran was busy tending the wounded. Instead of telling her to go away when she followed him around, or calling her a pest as he had been prone to do only a month before, he would stop what he was doing to hold her hand as she guided him about on little rambling walks through the ice.
Sokka and Katara would sleep curled up in the same skins and he would hold her until she was done crying and had fallen asleep, hiccuping stray sobs.
One day, after their father had been gone for two months, Grangran sat them down and started talking about sorrow, and grief, and how much their father loved their mother, and asked if they knew where the old people went when they went out onto the ice. Before Sokka or Katara could figure out what the heck she was talking about their father walked into camp, his face haggard, the carcass of an enormous musk caribeaver on his sled. He walked over to where his children stood and picked them up, hugging them tightly. Katara was only five and started to squirm after a second, but when he put them down, Sokka could see tears on his father's cheeks.
"Never mind, children," said Grangran, and gently shooed them off to play.
Sokka was twelve before he understood what Grangran had been talking about, and fifteen and at the opposite end of the earth before he understood why she had cause to worry.